Iranian Journal of

Background and Objectives: Increased growing nuclear industry has increased the researchers concerns on uranium presence in the environment and its effects on human health. Uranium is a dangerous radioactive heavy metal with high half-life and chemical toxicity. Therefore, the main objective of this study was to removal uranium (VI) from aqueous solution by uranium benzamide complex using AC_Fe3O4 nanocomposite. Materials and Methods: AC_Fe3O4 nanocomposite was synthesized using co-precipitation method. The experiments were designed as one factor at the time method. The optimum range of pH, contact time, amounts of adsorbent, and concentration of benzamide were determined. Then, kinetic and isotherm of uranium adsorption were studied. In addition, the properties of this adsorbent were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Results: The SEM and FTIR analysis confirmed that activated carbon is coated with Fe3O4 nanoparticles and the magnetic property of AC-Fe₂O₃ was approved. According to the results, the optimum conditions were pH =6, contact time =30 min, and 0.06 g of adsorbent dose. The adsorption of uranium on the AC_Fe₃O₄ nanocomposite fitted to Langmuir isotherm and pseudo-second order kinetic model. The removal of U(VI) was increased about 6% with increasing in benzamide concentration to 50 mg/L. The best percentage removal of uranium in aqueous solution was 95%. Conclusion: The removal of U(VI) on AC_Fe₃O₄ nanocomposite with the aid of benzamide is a rapid and highly pH depended process. The maximum sorption capacity (15/87 mg/g) of AC_Fe₃O₄ nanocomposite shows that this method is a suitable method for Uranium removal.

Background and Objective: Nitrate is one of the dissolved anions having great health importance in water. Human activities and natural sources are considered as the main roots of nitrate intrusion in to water bodies. The main objective of this paper was to study nitrate removal by packed bed column filled with (PAN)-oxime-nano Fe₂O₃. Materials and Methods: PAN-oxime-nano Fe₂O₃ were synthesized and used as an adsorbent in glass column for the removal of nitrate from aqueous solution. Nitrate solution tank was set above the prepared column. The effect of factors, such as flow rate (2, 5, and 7 mL/min) and bed depth (5, 10, and 15 cm) were studied. Results: It was found that the data fit well with Thomas model and breakthrough curve was designed accordingly. The column performed well at lowest flow rate. As the flow rates and time increased, earlier breakthrough was observed. The column breakthrough time (C_e/C₀ = 0.05) was reduced from 9 to 4 h, as the flow rates increased from2 to 7 mL/min. Conclusion: fixed-bed using PAN-oxime-nano Fe₂O₃ exhibited good removal of nitrate. The adsorption studies showed that at longer bed depth, better removal of nitrate would be achieved. Thomas model was suitable for the normal description of breakthrough curve at the experimental condition. The data also were in good agreement with logistic regression.

Background and Objective: Phenol and phenol derivatives in industrial wastewater are among the pollutants with priorities. The high cost and low efficiency of some routine treatment processes of industrial wastewater has limited their use. One of the new methods under consideration is, nowadays, adsorption using carbon nanotubes. This study was conducted in order to evaluate the application of alumina-coated multiwall carbon nanotubes in eliminating phenol from synthetic wastewater. Materials and Methods: This study was performed in laboratory at batch scale. Multi-wall carbon nanotubes were coated with Alumina. The concentration of phenol was determined by spectrophotometer through photometry. The effect of pH changes, dosage of adsorbent, contact time, the initial concentration of phenol, temperature, and the concentrations of different salts on the efficiency of absorption was evaluated. Then, the absorption results were described using the Langmuir and Freundlich isotherms and the synthetics of absorption. Results: It was found that absorption efficiency increased significantly by decreasing the initial concentration of phenol and pH and by increasing the carbon nanotube dosage, temperature, and contact time. On the other hand, the maximum elimination of phenol from the solution (98.86%) occurred at 4 mg/l phenol concentration, under acidic conditions (pH=3), at adsorbent dosage of 0.05 g/l, at temperature of 45°C, and contact time of 10 min. Evaluation of the regressions isotherms showed that the process follows the Langmuir model and second-degree synthetic absorption. Conclusion: The high efficacy (98%) of the adsorption process in this study showed that alumina-coated multiwall carbon nanotubes have a good capability in eliminating phenol and can be used as an appropriate and new method for eliminating phenol and its derivatives from wastewater.

Background & Objectives: Polycyclic aromatic hydrocarbons (PAHs) are considered as important organic contaminants due to their high toxicity and carcinogenic properties. Among PAHs, phenanthrene is found in most contaminated sites. Sorption and desorption of phenanthrene in soil affect the fate of the contaminant in soil-water system. Presence of organic matter (OM) in the soil matrix can also affect sorption and desorption of phenantherene. In this research, effect of soil organic matter on sorption of phenanthrene in kaolin soil was studied. Materials & Methods: The sorption of sorption of phenanthrene in kaolin clay was assessed in the presence and absence of organic matter. These two soil types were used in batch sorption experiments of Phenanthrene to determine the sorption properties. Results: It was found that organic matter increases the cation exchange capacity, water content, and pH of the soil. Sorption of phenantherene in both kaolin and OM-added kaolin was better fitted with Freundlich linear model. Moreover. soil organic matter increased phenanthrene sorption in soil. Conclusion: It was observed that with 41.04% increase in OM, distribution coefficient of phenanthrene sorption in soil increased by 36.69%.

Objective and Background: Fluoride is an element widely found in the earth crust. Advantages and disadvantages of fluoride in the human body are depended on its concentration. Long-term consumption of drinking water contaminated with arsenic can cause adverse health effects such as skin lesions and cancer in humans. The aim of this study was to study efficiency of nano alumina on multi walled carbon nano tube  for removal As(V) and fluoride from aqueous solution.

Materials and Method: In this study, nano-scale crystalline alumina was synthesized on single walled carbon nanotube by sol-gel method for using as a sorbent for solid phase extraction of Fluorine ion and arsenic(V). Response surface methodology based on Box-Behnken was used to assess the effect of independent variables on the response function and prediction of the best response value. In this study, effect of different parameters, such as contact time (10 to 120 min), pH (3-9), adsorbent dosage (0.25-1.5 g/L) and initial concentration of fluoride (2-8 mg/L) on efficiency of process was investigated. The structure of nano-scale alumina on multi walled carbon nano tube was determined by XRD and SEM techniques. Moreover, Freundlich and Langmuir isotherm models were used to calculate equilibrium constant.

Results: It was found that by increasing contact time and adsorbent dosage the rate of fluoride removal increased. However, by increasing pH and initial concentration the efficiency of fluoride removal decreased. High value for R² (0.94) shows that removal of arsenic(V) can be described by this model. The Freundlich isotherm was the best fitted graph for experimental data with R² more than 0.997.

Conclusion: In this study, it was observed that efficiency of arsenic(V) and fluoride  removal was greatly increased by using nano-scale alumina on multi walled carbon nanotubes (MWCNTs).

Background and Objectives: Rapid growing of Triton X-100 application in industries results in its appearance in effluents  and threaten the aqueous ecosystems. Triton X-100 is not biodegradable and can accumulate in food chain.

Materials and Methods: In this study, sorption capacity of six synthesized zeolites with different regular porous structure was studied for triton X-100 (TX-100) surfactant and the results were compared with Clinoptilolite natural zeolite of Damavand region.

Results: Within all zeolite studied, Beta(200) showed the highest sorption capacity (about 575 mg/g), which is due to its regular pore structure with large pore diameter, channel intersections, high SiO₂/Al₂O₃ ratio and high surface area. Langmuir monolayer isotherm and pseudo-second-order kinetic equation could provide well-fitted to the experimental data in simulating adsorption behavior of TX-100 over Beta(200) zeolite.

Conclusion: The adsorption feature was internal sorption and the intraparticle diffusion might be a rate-limiting control for Beta(200) zeolite. Results of experiments demonstrated that the hydrophobic zeolites with large pore diameter such as Beta(200) could be effective sorbents for industrial wastewater treatment features.

Background and Objectives: Furfural is one of the toxic chemical compounds used in many industries such as petrochemical, food, paper products, pharmaceutical, etc., due to having some characteristics. Therefore, furfural could be found at different concentrations in the effluent from these industries and can enter the environment. Hence, the aim of this study was the assessment the efficiency of a low cost bentonite modified with cationic surfactant in the removal of furfural from aqueous solution.

Material and Methods: In this experimental study, bentonite was purchased from one of the Mines of Zanjan Province, Iran and then the efficiency of bentonite modified with the cationic surfactant CTAB (CTAB-Bent) was assessed in the adsorption of furfural from aqueous solution. Activated carbon (AC) was also purchased as commercial grade.

Results: Under optimum conditions, the removal efficiency of AC and CTAB-Bent was about 52 and 66%, respectively. For both adsorbents used in this study, the increase of contact time and sorbent dosage resulted in increasing the removal efficiency, but the removal efficiency was decreased with the increase of furfural initial concentrations. Regarding pH, the removal efficiency was the highest in relative acidic and neutral environment, (60 and 69% for AC and CTAB-Bent respectively). The kinetics studies revealed that the highest correlation coefficients were obtained for the pseudo-second order rate kinetic model. Adsorption data from both adsorbents was also fitted with Langmuir isotherm.  

Conclusion: It was found that modified bentonite with CTAB as a natural adsorbent could have better efficiencies compared with activated carbon in the furfural removal, although more contact times is needed.

Background and Objectives: In this work, biosorption of hexavalent chromium from aqueous solution with excess municipal sludge was studied. Moreover, the performance of neural networks to predict the biosorption rate was investigated.

Materials and Methods: The effect of operational parameters including initial metal concentration, initial pH, agitation speed, adsorbent dosage, and agitation time on the biosorption of chromium was assessed in a batch system. A part of the experimental results was modeled using Feed-Forward Back propagation Neural Network (FFBP-ANN). Another part of the test results was simulated to assess the model accuracy. Transfer function in the hidden layers and output layers and the number of neurons in the hidden layers were optimized.

Results: The maximum removal of chromium obtained from batch studies was more than 96% in 90 mg/L initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/L. Maximum biosorption capacity was 41.69 mg/g. Biosorption data of Cr(VI) are described well by Freundlich isotherm model and adsorption kinetic followed pseudo-second order model.  Tangent sigmoid function determined was the most appropriate transfer function in the hidden and output layer. The optimal number of neurons in hidden layers was 13. Predictions of model showed excellent correlation (R=0.984) with the target vector. Simulations performed by the developed neural network model showed good agreement with experimental results.

Conclusion: Overall, it can be concluded that excess municipal sludge performs well for the removal of Cr ions from aqueous solution as a biological and low cost biosorbent. FFBP-ANN is an appropriate technique for modeling, estimating, and prediction of biosorption process If the Levenberg-Marquardt training function, tangent sigmoid transfer function in the hidden and output layers and the number of neurons is between 1.6 to 1.8 times the input data, proper predication results could be achieved.

Background and Objective: Arsenic is one of the most toxic pollutants in groundwater and surface water. Arsenic could have lots of adverse impacts on human health. Therefore, access to new technologies is required to achieve the arsenic standard.

Materials and Methods: The present study was conducted at laboratory scale in non-continuous batches. The adsorbent of zero-valent iron nanoparticles -Chitosan was produced through reducing ferric iron by sodium borohydride (NaBH₄) in the presence of chitosan as a stabilizer. At first, the effect of various parameters such as contact time (5-120 min), pH (3-10), adsorbent dose (0.3-3.5 g/L) and initial concentration of arsenate (2-10 mg/L) were investigated on process efficiency. Then optimum conditions in terms of contact time, pH, adsorbent dose and initial concentration of arsenate were determined by RSM method. Freundlich and Langmuir isotherm model equilibrium constant, pseudo-first and second order kinetic constants were calculated. The residual arsenate was measured y using ICP-AES.

Results: The optimum values based on RSM for pH, absorbent dose, contact time, and initial concentration of arsenate were 7.16, 3.04 g/L, 91.48 min, and 9.71 mg/L respectively. Langmuir isotherm with R²= 0.9904 for Arsenate was the best graph for the experimental data. According to Langmuir isotherm model, the maximum amount of arsenate adsorption was 135.14mg/g. . The investigation of arsenate adsorption kinetics showed that arsenate adsorption follows the pseudo-second kinetics model.

Conclusion: This research showed that the adsorption process is depended on pH. With increasing pH, the ability of amine groups in chitosan are decreased to protonation, caused to decrease the efficiency of arsenate removal at high pH.

Background and Objectives: Adsorption is one of the most common methods for VOCs elimination from waste air stream. The study on the application of a selective and cheap adsorbent with high efficiency in VOCs removal is important from economic aspects. In this study, the potential of MnO/GAC and MgO/GAC composites was investigated for toluene adsorption from air stream at  lab scale.

Material and methods: The MnO/GAC and MgO/GAC adsorbents were prepared through Sol-gel method and then were characterized using BET, XRF, and SEM analysis. The effect of operational parameters including; retention time (0.5, 1, 1.5, 2, and 4 S), inlet toluene concentration (100, 200, 300, and 400 ppmv) and the temperature of the air stream (25, 50, 75, and 100 ˚C) were examined on the efficiency of both adsorbents. The efficiency of MnO/GAC and MgO/GAC were determined from the breakthrough time and adsorption capacity and the results were compared statistically.

Results: The breakthrough time of MnO/GAC and MgO/GAC adsorbents increased 90% by increasing retention time from 0.5 to 4 S. Adsorption capacity of MgO/GAC and MnO/GAC was increased 39and 61.1% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. Breakthrough time of MgO/GAC and MnO/GAC decreased 65 and 59% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. The efficiency of MgO/GAC and MnO/GAC adsorbents had a direct relationship with the increase of air temperature from 25 to 100 ˚C. Accordingly, the efficiency of MgO/GAC and MnO/GAC was increased 78 and 32% by increasing air temperature, respectively.  

Conclusion: The results of the study showed that MgO/GAC and MnO/GAC adsorbents had high efficiency in toluene removal from air stream. The difference between the efficiency of MgO/GAC and MnO/GAC adsorbents was significant and MgO/GAC adsorbent showed higher efficiency than MnO/GAC for toluene adsorption from waste air.  

Background and Objectives: Heavy metals are seriously dangerous for the human body and their accumulation in the body can cause pathological changes in the organs and this can result in cardiovascular, liver and bone diseases, and even cancer. Human is exposed daily to these pollutants via consumption of food and water.

Materials and Methods: Considering the cumulative properties of these metals in plant organs, the amount of Cr, Mn, and Fe in soil and leaf, stem, and root tissues of cabbage, lettuce, spinach, and onions in Karaj City were investigated. For this purpose, 15 samples were randomly collected from each part of the plants, and then, the density of heavy metals was measured via atomic absorption spectrometer after cleansing, grinding, drying, and acid digestion. The data were then analyzed using SPSS software.

Results: It was found that leaves of spinach, cabbage, lettuce, and onion have higher concentrations of Cr, Mn, and Fe rather than their stems and roots. The roots of plants contain the least densities of metals. Moreover, concentrations of Fe, Cr, and Mn in soil were 11.87, 3.99 and 17.78 mg/kg, respectively. This was due to the high transportation of these metals to air-related parts of the plant like leaves. This research also showed that the densities of Cr, Mn, and Fe in leaves of studied spinach, onion, cabbage, and lettuce exceeded the FAO/WHO standard limitations (0.15, 0.3, and 0.3 mg/kg for Cr, Fe and Mn, respectively).

Conclusion: Due to the high concentrations of Cr, Mn, and Fe in studied vegetables in Karaj City, the consumption of these kinds of vegetables by citizens must be taken into consideration by regulatory agencies.

Background and Objective: Dyes are important pollutants that lead to producing serious hazards to human, other animals and organisms. Dyes are not biodegradable by aerobic treatment processes. Therefore, their removal from industrial effluents before discharging into the environment requires extreme and great attention. The aim of this research was to evaluate removal efficacy of methyl orange dye from aqueous solutions using NiFe₂O₄ nanoparticles.

Materials and Methods: This study was an empirical investigation in which NiFe₂O₄ nanoparticles were synthesized by co-precipitation method and were used as an adsorbent for the removal of methyl orange from aqueous solution. NiFe₂O₄ nanoparticles were characterized using X-Ray Diffraction (XRD), Transmission Electronic Microscopy (TEM), pH_pzc and SEM-EDX elemental analysis methods. Experiments were conducted discontinuously using 20 mL methyl orange solution of 40 mg/L. The effect of variables such as pH (2-8), amount of adsorbent (0.009-0.07 g) and contact time (2-70 min) on the efficacy of dye removal was studied. Finally, experimental data were compared by Langmuir, Freundlich, and Temkin isotherms and pseudo-first-order and pseudo-second-order kinetic models.

Results: TEM images showed that the NiFe₂O₄ nanoparticles had spherical shapes with the size of 12 nm. The results indicated that removal efficiency increased up to 0.04 g adsorbent and 20 min contact time. The optimum pH for methyl range removal was 2. Moreover, under these conditions, the adsorption process followed the Langmuir adsorption isotherm with a correlation coefficient of 0.995 and pseudo-second-order kinetic model with a correlation coefficient of 0.999. Also, the maximum adsorption capacity of the prepared adsorbent was 135 (mg/g) for Langmuir isotherm.

Conclusion: The NiFe₂O₄ nanoparticles are effective and available adsorbents for the removal of methyl orange from industrial wastewater.

Background and Objectives: Fluoride has both beneficial and detrimental effects on health. Therefore, it is important to determine its concentration in drinking water. Dental fluorosis and skeletal fluorosis are health effects caused by long term exposure to high levels of fluoride in drinking water. The aim of this research was to investigate fluoride removal using modified diatomite-supported ferric oxide nanoparticles and to determine the adsorption kinetics and isotherm.

Materials and Methods: This fundamental and practical study was performed at laboratory scale. The effects of pH (3.5-9.5), contact time (20-100 min), adsorbent dosage (1-5 g/L), and initial concentrations of fluoride (5-25 mg/L) on the adsorption efficiency were evaluated. The properties of adsorbent were investigated using XRD, XRF, FTIR and FESEM. Finally, the suitability of pseudo first and second order kinetics, and Langmuir and Freundlich isotherms for the data were investigated.

Results: This study showed that the removal efficiency of F^- increased with increase in contact time, decrease in pH, increase in adsorbent dose, and increase in initial fluoride concentration. The highest removal efficiency was observed at pH=3.5, 60 minutes contact time, and 3 g/L of adsorbent dose in the initial concentration of 5 mg/L F^-. Pseudo first order and Freundlich were the best fitted kinetic and isotherm models, respectively, for describing F^- adsorption process.

Conclusion: The present study indicates that the modified diatomite-supported ferric oxide nanoparticles can be used as an effective and environmentally friendly biosorbent for the removal of fluoride ions from aqueous solutions.

Background and Objective: Surfactants can be found in soaps, detergents, pharmaceutical products, personal care products, as well as in leather industries. In this study, adsorption of Sodium Dodecyl Sulfate (SDS) on magnetic multi-walled carbon nanotubes in the aqueous solutions was investigated.

Materials and methods: Surfactant concentration, adsorbent dosage, and pH values were considered as variables. Residual surfactant was measured using methylene blue method and adsorbent characteristic was determined by X-Ray diffraction and Fourier transform infrared spectroscopic analysis. Adsorption capacity, adsorption isotherm, and kinetic reaction were also investigated.

Results: Adsorption investigations demonstrated that the increase in initial SDS concentration or pH values, led to the decrease in SDS adsorption. Conversely, the same result was achieved by decreasing adsorbent dosage. After 120 min SDS adsorption became stable. By increasing in SDS concentration from 15 to 150 mg/L, adsorption capacity improved from 8 to 61 mg/g. Isotherm and kinetic data demonstrated that experimental data pursued Langmuir isotherm (R²=0.993) and pseudo-second order equation (R²=0.992).

Conclusion: Magnetic multiwall carbon nanotubes can be used as an effective and useful sorbent for SDS removal due to several advantages including: high adsorption capacity, relatively low equilibrium time, and easy separation of magnetic multiwall carbon nanotubes from aqueous solutions.

Background and Objective: Nicotine as the most toxic alkaloid in tobacco is one of the compounds which causes human death over the past few decades. The purpose of this paper was to remove nicotine environmental pollution from aqueous solutions using halloysite-polythiophene nanocomposite. 

Materials and Methods: Halloysite-polythiophene nanocomposite was prepared using a homogeneous solution of HNT and FeCl₃ at 0-5°C by the ball milling technique. In this study, parameters such as pH, contact time and initial concentration of nicotine in laboratory scale were studied and the physical properties of the adsorbent were characterized via fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Then, the absorption results were described using Langmuir and Freundlich isotherms.

Results: The results showed that the pH, initial concentration of nicotine and contact time had a direct effect on the nicotine adsorption process. The adsorption of nicotine followed Langmuir isotherm (R² < 0/995). Moreover, the best adsorption result was achieved at pH=7, 50mg adsorbent, contact time of 90 min and 50mg/L of nicotine.

Conclusion: The results of this study showed that the Halloysite modification as a mineral composite with polythiophene and the synthesis of HNT@PTh nanocomposite can be used as an effective adsorbent to adsorb the nicotine.

Background and Objective: Phosphorus (P), as one of the agricultural, industrial and urban wastewater pollutants, plays an important role in eutrophication of surface waters. Use of cationic sorbents for removal of anions including phosphate from aqueous environments is a well-known and effective method. Meanwhile, layered double hydroxides (LDHs) are known as effective anion exchange sorbents. In this study, the efficiency of Mg-Al layered double hydroxide (Mg-Al-LDH) for P removal from aqueous solutions was investigated.

Methods and Materials: The Mg-Al layered double hydroxide (Mg-Al-LDH) was synthesized by co-precipitation method and used for removing of P from aqueous solutions. The kinetics and equilibrium studies of phosphate adsorption by Mg-Al-LDH were performed using a batch experiment at different contact times, initial phosphate concentrations, pH values, ionic strengths and doses of sorbent.

Results: The results of the kinetics experiments showed that sorption of P with LDH reached equilibrium after 30 min. The highest correlation coefficient was obtained for the pseudo-second order model, indicated that chemical sorption controlled the rate of phosphate sorption by LDH. The results showed that the sorption experiments data were in good agreement with Langmuir model and the maximum adsorption capacity predicted by this model was 37.83 mg P/g LDH.

Conclusion: The current study revealed that P adsorption by LDH was increased by increasing contact time and concentration of LDH, but decreased by increasing initial concentration of P, pH and ionic strength. The optimum conditions for phosphate anion adsorption by Mg-Al-LDH were determined as P initial concentration of 20 mg/L, contact time of 120 min, pH of 3.0, sorbent dose of 10 g/L and ionic strength of 0.03 mol/L.